docs: def is_protein_package(self):
          '''Return true if this package is an Amino Acid alignment package, otherwise
          False i.e. it is a nucleotide package. Cache the result for speed.
  
          '''
          if not hasattr(self, '_is_protein_package'):
              self._is_protein_package = GraftMPackageVersion3.graftm_package_is_protein(self)
          return self._is_protein_package